Question

Where is the top of the asthenosphere is closest to earth's surface ________?

Answer 1

The top of the asthenosphere is closest to the earth's surface underneath OCEANIC CRUST. The asthenosphere is the area of the mantle beneath the lithosphere that is solid, but hotter than the rock above it. This layer can low under pressure and function as a soft , weak zone over which the lithosphere may move. 

of the two types of crust, continental and oceanic; the latter is the thinnest. oceanic crust can be as little as 5km thick while continental crust can be up to 90km thick at the mountain ranges.